1. Field of the Invention
The present invention relates to a method of etching a magnetic layer made of high saturated flux density materials, a method of forming a magnetic pole of a thin film magnetic head having at least an inductive-type magnetic transducer for writing and a method of manufacturing a thin film magnetic head.
2. Description of the Related Art
Performance improvement in thin film magnetic heads has been sought in accordance with an increase in surface recording density of a hard disk device. A composite thin film magnetic head, which is made of a layered structure including a recording head with an inductive-type magnetic transducer for writing and a reproducing head with a magnetoresistive (MR) element for reading, is widely used as a thin film magnetic head. As MR elements there are an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) that utilizes the GMR effect. A reproduction head using the AMR element is called an AMR head or simply an MR head. A reproducing head using the GMR element is called a GMR head. The AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. The GMR head is used as a reproducing head whose surface recording density is more than 3 gigabit per square inch.
The AMR head includes an AMR film having the AMR effect. In the GMR head, the AMR film is replaced with a GMR film having the GMR effect and the configuration of the GMR head is similar to that of the AMR head. However, the GMR film exhibits a greater change in resistance under a specific external magnetic field compared to the AMR film. Therefore, the reproducing output of the GMR head is about three to five times as great as that of the AMR head.
The MR film may be changed in order to improve the performance of a reproducing head. In general, the AMR film is made of a magnetic substance that exhibits the MR effect and has a single-layered structure. In contrast, many of the GMR films have a multi-layered structure consisting of a plurality of films. There are several types of mechanisms which produce the GMR effect and the layer structure of the GMR film changes depending on the mechanism. The GMR films include a superlattice GMR film, a granular film, a spin valve film and so on. The spin valve film is most efficient for the GMR film which has a relatively simple structure, exhibits a great change in resistance in a low magnetic field, and is suitable for mass production. The performance of a reproducing head is thus easily improved by, for example, changing the MR film from the AMR film to the GMR film and so on which are the materials with an excellent magnetoresistive sensitivity.
As a primary factor for determining the performance of a recording head, there is a pattern width, especially an MR height, in addition to the selection of a material described above. The MR height is the length (height) between the end of an MR element closer to an air bearing surface and the other end. The MR height is originally controlled by an amount of grinding when the air bearing surface is processed. The air bearing surface (ABS) here is a surface of a thin film magnetic head that faces a magnetic recording medium and is also called a track surface.
Performance improvement in a recording head has also been expected in accordance with the performance improvement in a reproducing head. It is required to increase the track density of a magnetic recording medium in order to increase the recording density among the performance of a recording head. In order to achieve this, a recording head of a narrow track structure in which the width of a bottom pole and a top pole being formed sandwiching a write gap on the air bearing surface is required to be reduced to the order of few microns to submicron. Semiconductor process technique is used to achieve the narrow track structure.
Another factor for determining the performance of a recording head is the throat height (TH). The throat height is the length (height) of a portion (magnetic pole portion) which is from the air bearing surface to an edge of an insulating layer which electrically isolates the thin film coil. Reducing the throat height is desired in order to improve the performance of a recording head. The throat height is also controlled by an amount of grinding when the air bearing surface is processed.
In order to improve the performance of a thin film magnetic head, it is important to form a recording head and a reproducing head in well balance as described.
Here, a cross sectional configuration of a composite thin film magnetic head as an example of a thin film magnetic head of the related art is described with reference to FIG. 28A and FIG. 28B. In FIG. 28, xe2x80x9cAxe2x80x9d shows a cross section vertical to a track surface and xe2x80x9cBxe2x80x9d shows a cross section of a magnetic pole portion parallel to the track surface. The magnetic head 100 comprises a magnetoresistive reading head portion (called a reading head portion in the following) 100A for reproducing and an inductive recording head (called a recording head in the following) 100B for recording.
The reading head portion 100A is a pattern of a magnetoresistive layer (called an MR layer in the following) 105 being formed on a substrate 101 made of, for example, ALTIC (Al2O3xc2x7TiC) through an undercoating layer 102 formed with, for example, alumina (aluminum oxide, Al2O3), a bottom shield layer 103 formed with, for example, ferrous aluminum silicide (FeAlSi), and a shield gap layer 104 formed with, for example, aluminum oxide (AM20., called alumina in the following) in order. Further, a lead terminal layer 105a made of a material which does not diffuse into the MR films such as tantalum (Ta), tungsten (W) and so on is formed on the shield gap layer 104. The lead terminal layer 105a is electrically connected to an MR layer 105. The MR layer 105 is formed with various kinds of materials having magnetoresistive effect such as permalloy (NiFe alloy), nickel (Ni)xe2x80x94cobalt (Co) alloy and so on. A shield gap layer 106 made of, for example, alumina is laminated on the MR layer105 and the lead terminal layer 105a. That is, the MR layer 105 and the lead terminal layer 105a are buried between the shield gap layers 104 and 106.
The recording head portion 100B comprises a top pole 109a being formed on the reading head portion 100A through a bottom pole 107 which functions as a top shield layer of the MR layer 105 and a gap layer 108. An insulating layer 110 is formed on the gap layer 108, and a first layer of a thin film coil 111 and a second layer of a thin film coil 112 are laminated on the insulating layer 110. The thin film coils 111 and 112 are respectively formed on the shield layers lila and 112a by plating method. The thin film coils 111 and 112 are covered with the insulating layers 113 and 114. A top pole layer 109 including the top pole 109a is formed on the insulating layers 110, 113 and 114. The top pole layer 109 is covered with an overcoat layer 115. In the recording head portion 100B, a bottom pole 107a facing the top pole 109a has a trim structure in which part of the surface of the top shield layer 107 is processed to be protruded.
In the magnetic head 100, reading-out of information from a magnetic disk which is not shown in figure is performed in the recording head portion 100A using magnetoresistive effect of the MR layer 105, while writing of information to a magnetic disk is performed in the recording portion 100B using a change in magnetic flux between the top pole 109a and the bottom pole 107a. 
FIG. 29A and FIG. 29B to FIG. 38 show an example of a method of manufacturing another composite thin film magnetic head of the related art.
First, as shown in FIG. 29A and FIG. 29B, an insulating layer 202 made of, for example, alumina (aluminum oxide, Al2O3) of about 5-10 xcexcm in thickness is deposited on a substrate 201 made of, for example, altic (Al2O3xc2x7TiC).
Next, as shown in FIG. 30A and FIG. 30B, a bottom shield layer 203 for a reproducing head is formed on the insulating layer 202.
Next, as shown in FIG. 31A and FIG. 31B, a shield gap film 204 is formed on the bottom shield layer 203 by depositing, for example, alumina about 40-50 nm in thickness. Next, an MR film 205 of tens of nanometers in thickness for composing an MR element for reproduction is formed on the shield gap film 204, and photolithography with high precision is applied to obtain a desired shape.
Next, as shown in FIG. 32A and FIG. 32B, a shield gap film 206 is formed on the shield gap film 204 and the MR film 205, and the MR film 205 is buried in the shield gap films 204 and 206.
Next, as shown in FIG. 33A and FIG. 33B, a top shield-cum-bottom pole (called a bottom pole in the following) 207 made of, for example, permalloy (NiFe) which is a magnetic material used for both the reproducing head and the reading head is formed on the shield gap film 206. Next, a write gap layer 208 made of insulating film such as alumina film is formed on the bottom pole 207. Further, an opening for connecting the top pole and the bottom pole is formed through patterning the write gap layer 208 by photolithography. Next, a pole tip 209 and a connecting portion pattern 209a of the top pole and the bottom pole is formed with a magnetic material made of permalloy (NiFe) by plating method. The bottom pole 207 and a top pole 216 which is to be described later are connected through the connecting portion pattern 209a so that forming a through-hole after CMP (Chemical and Mechanical Polishing) which is to be described later becomes easier. Next, the write gap layer 208 and the bottom pole 207 are etched about 0.3-0.5 xcexcm by ion milling using the pole tip 209 as a mask. By etching the bottom pole 207, widening of effective writing track width can be suppressed (that is, spread of magnetic flux in the bottom pole can be suppressed when writing data).
Further, as shown in FIG. 34A and FIG. 34B, an insulating film 210 of about 3 xcexcm in thickness made of, for example, alumina is formed all over the surface before flattening the whole surface by CMP. Then, a photoresist film 211 is formed on the insulating film 210 by photolithography with high precision. Next, a first layer of a thin film coil 212 for an inductive-type recording head made of, for example, copper (Cu) is selectively formed on the photoresist film 211 by, for example, plating method.
Next, as shown in FIG. 35A and FIG. 35B, a photoresist film 213 is formed in a desired pattern on the photoresist film 211 and the thin film coil 212 by photolithography with high precision. Further, a heat treatment is applied so as to flatten the thin film coil 212 and to isolate the turns of the thin film coil 212 from each other.
Next, as shown in FIG. 36A and FIG. 36B, a second layer of a thin film coil 214 made of for example, copper is formed on the photoresist film 213 by, for example, plating method. Next, a photoresist film 215 is formed in a predetermined shape on the photoresist film 213 and the thin film coil 214 by photolithography with high precision. A heat treatment is applied so as to flatten the thin film coil 214 and to isolate the turns of the thin film coil 214 from each other.
Next, as shown in FIG. 37A and FIG. 37B, a top yoke-cum-top pole (called a top pole in the following) 216 made of a magnetic material such as permalloy for a recording head is formed on the pole tip 209, the photoresist films 211, 213 and 215. The top pole 216 has a contact with the bottom pole 207 in a rear position of the thin film coils 212 and 214, and is magnetically coupled to the bottom pole 207. Further, an overcoat layer 217 made of, for example, alumina is formed on the top pole 216. At last, a thin film magnetic head is completed after forming a track surface (air bearing surface) 218 of a recording head and a reproducing head by performing a machine processing on a slider.
FIG. 38 and FIG. 39 show a complete state of a thin film magnetic head. FIG. 38 shows a cross section of a thin film magnetic head vertical to the track surface 218 and FIG. 39 shows an enlarged cross section of the pole portion parallel to the track surface 218. In FIG. 38, TH represents the throat height and MR-H represents the MR height. Further, in FIG. 39, P2W represents a pole width and P2L represents a pole thickness.
As an factor for determining the performance of a thin film magnetic head, there is an apex angle as represented by xcex8 in FIG. 38 besides the throat height, the MR height and so on. The apex angle is an angle between a line connecting a corner of the side surface on the track surface side of the photoresist films 211,213 and 215, and the upper surface of the top pole 216.
As shown in FIG. 39, a structure in which part of each sidewall of the pole tip 209, the write gap layer 208 and bottom pole 207 is formed in a self-aligned manner is called a trim structure as described above. With the trim structure, increase of the effective track width caused by spread of the magnetic flux occurred while writing of the narrow track can be suppressed. Further, as shown in FIG. 39, a lead layer 205a is provided on the side of the MR film 205.
To improve the performance of a thin film magnetic head, it is important to precisely form the throat height TH, the MR height MR-H, the apex angle xcex8, the track width (pole width) P2W and the pole length P2L as shown in FIG. 38 and FIG. 39.
In this application, problems regarding controls of the track width is being focused specifically.
The track width P2W is required to be precisely formed since it determines the track width of a recording head. Especially these days, for enabling high surface density writing, that is to form a recording head with a narrow track structure, measurement of 1.0 xcexcm or less is required. In order to achieve this, the pole tip 209 and the top pole 216, which determine the track width, are required to be minutely formed.
As a method of forming a top pole, frame plating method is used as claimed in, for example, Japanese Patent Application Laid-open Hei 7-262519. In a case where the top pole is formed using frame plating method, first, a thin electrode film (not shown in figure) made of, for example, permalloy is formed all over the coil portion (called apex area) which is protruded like a mountain by being covered with the photoresist films (for example, photoresist films 110, 113 and 114 in FIG. 28A and FIG. 28B). Next, a frame (outer frame) for plating is formed through applying photoresist on the electrode film and patterning it by photolithography. Further, the top pole is formed by plating method having the electrode film formed earlier as a seed layer.
By the way, there is a difference of 7-10 xcexcm or more in heights in the apex area. Photoresist of 3-4 xcexcm in thickness is applied onto the apex area. If the film thickness of the photeresist on the apex area is required to be at least 3 xcexcm or more, a photo resist film of about, for example, 8-10 xcexcm or more in thickness is formed in the lower part of the apex area since photoresist with liquidity gathers in a lower area.
To form a narrow track as described above, a pattern of about 1.0 xcexcm in width is required to be formed by the photoresist film. Accordingly, a micro pattern of about 1.0 xcexcm in width is required to be formed by the photoresist film of 8-10 xcexcm or more in thickness, however, it is extremely difficult.
Further, during exposure of photolithography, a light for the exposure reflects by the electrode film made of, for example, permalloy and the photoresist is exposed also by the reflecting light resulting in deformation and so on of the photoresist pattern. As a result, the top pole can not be formed in a desired shape, which means, for example, its sidewalls take a round-shape and so on. As described, it is extremely difficult with the related art to form the top pole with high precision for obtaining a narrow track structure by precisely controlling the track width P2W.
For the reasons described, as shown in FIG. 29A and FIG. 29B to FIG. 37A and FIG. 37B, a method of connecting the pole tip 209 and the top pole 216, which is to be a yoke, after forming a track width of 1.0 xcexcm or less on the pole tip 209, which is effective for forming the narrow track of the recording head, is used. That is, a method of dividing the top pole 109 (FIG. 28A and FIG. 28B) into the pole tip 209 for determining the track width and the top pole (yoke) 216 for inducing the magnetic flux is employed.
However, there are problems as follows especially on the recording head side, even in a thin film magnetic head manufactured through the method as described. As a result, performance improvement of the recording head may be suppressed.
That is, ion milling used in a case where a narrow track is formed by etching a magnetic layer (pole tip 209 in FIG. 33A and FIG. 33B). However, during the procedure, the photoresist is also etched by a large amount through ion milling since the photoresist is used as a mask. Accordingly, there is a problem that a large difference in the etching profile in the etched magnetic layer occurs. As a result, the pole tip 209 takes a shape with taper so that control of micro measurement such as half-micron or micro-micron is substantially impossible. Further, in a case where the photoresist film is used as a mask of the magnetic layer, a light for exposure reflects from the magnetic layer during photolithography and the photoresist is exposed also by the reflecting light resulting in a problem that exposure precision is deteriorated.
To overcome such problems of the photoresist mask, a method of manufacturing a thin film magnetic head in which an inorganic material is used for a mask of the magnetic layer (Japanese Patent Laid-open Hei 2-44511) is proposed. In the method, an inorganic mask layer is formed on the top pole and an inorganic mask is formed through etching the mask layer by ion milling (ion beam) having the photoresist film as a mask. Further, the top pole is etched to a predetermined shape by ion milling (ion beam) through the inorganic mask.
With the method, the problems of a case where the photoresist mask described above is used are solved. However, in the method of the related art, there is a problem that the etching procedure of the inorganic mask takes too long and etching of the magnetic layer takes extremely a long time to complete, since the same ion milling method as the etching method of the magnetic layer is used in order to form the inorganic mask.
The invention is designed to overcome the foregoing problems. The object is to provide a method of etching a magnetic layer which is possible to control measurement of micro width of the magnetic layer while shortening the etching procedure, a method forming the magnetic pole of a thin film magnetic head and a method of manufacturing a thin film magnetic head.
A method of etching a magnetic layer of the invention includes the steps of. forming an inorganic insulating mm on the surface of the magnetic layer; forming a first mask on the surface of the inorganic insulating film; forming a second mask by selectively removing the inorganic insulating film through reactive ion etching using the first mask; and selectively removing the magnetic layer using the second mask.
A method of forming a magnetic pole of a thin film magnetic head of the invention is a method of forming a thin film magnetic head having two magnetic layers including a first magnetic pole and a second magnetic pole being magnetically coupled to each other, while part of sides of which facing a recording medium oppose each other through a write gap layer. The method includes the steps of: forming a magnetic layer corresponding to either the first or the second magnetic pole before forming an inorganic insulating film on a surface of the magnetic layer; forming a first mask on the surface of the inorganic insulating film; forming a second mask by selectively removing the inorganic insulating film through reactive ion etching using the first mask; and forming at least either the first magnetic pole or the second magnetic pole by selectively removing the magnetic layer using the second mask.
A method of manufacturing a thin film magnetic head of the invention is a method of manufacturing a thin film magnetic head having a first magnetic layer and a second magnetic layer made of at least one layer respectively including a first magnetic pole and a second magnetic pole being magnetically coupled to each other, while part of sides of which facing a recording medium oppose each other through a write gap layer, and a thin film coil provided between the first magnetic layer and the second magnetic layer. The method includes the steps of: forming a first magnetic layer corresponding to the first magnetic pole; forming a gap layer on the first magnetic layer; forming a thin film coil on the gap layer; and forming the second magnetic layer corresponding to the second magnetic pole; wherein: the step of forming the second magnetic layer includes the steps of: forming a magnetic layer corresponding to the second magnetic pole before forming an inorganic insulating film on a surface of the magnetic layer; forming a first mask on a surface of the inorganic insulating film; forming a second mask by selectively removing the inorganic insulating layer through reactive ion etching using the first mask; and forming at least a second magnetic pole by selectively removing the magnetic layer using the second mask.
In a method of etching a magnetic layer, a method of forming a magnetic pole of a thin film magnetic head and a method of manufacturing a thin film magnetic head of the invention, a second mask made of an inorganic insulating film is formed by reactive ion etching using a first mask, and etching of a magnetic layer (a second magnetic layer) is performed using the second mask.
The first mask is formed with, specifically, a photoresist film or a plating film. The inorganic insulating film is formed with, for example, aluminum oxide (alumina, Al2O3) or silicon dioxide (SiO2). The magnetic layer is preferable to be formed with a magnetic material with high saturation flux density such as permalloy (NiFe) and so on. Further, etching of the magnetic layer using the second mask is preferable to be performed by ion milling method.